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Repeated measures of horizontal heterophoria
1Visual Ergonomics Research Group (VISERG), Department of Human Sciences, Loughborough University, Leicestershire, United Kingdom. p.a.howarth@lboro.ac.uk
Purpose:
To assess repeatability, horizontal heterophoria measurements were taken from 31 subjects on five occasions, each between 1 and 4 weeks apart.
Method:
Distance heterophoria was measured using a Maddox Rod, and near heterophoria was measured using a Maddox Wing. In addition, near measurements were repeated with a +3.00 D lens in front of each eye to place the targets at optical infinity. In each case, the standard deviation of the five values was taken as a metric of the test variability.
Results:
On average, the variability of the Maddox Rod was half of the Maddox Wing, both with and without the lenses.
Conclusion:
This consistency suggests that the difference reflects the test conditions rather than optical differences in the target position.